On EEVblog #1078 Dave did a tear-down of a super-thin calculator that was held together almost exclusively with adhesive. Was this similar to the type of adhesive used in many modern phones and tablets? The type that you can use "heat-retaining bags" to loosen?
I was looking into designing some super-thin sensor boards and it seems like these adhesives are the only option if you want super-flat designs. My first question is -- is there a name for this category of adhesives? So far I've been using CA glue, but most CA glues I've used only "break" at over 350C, meaning it's a one-way process unless I want to effectively "reflow" the entire device if I want to take it apart.
The other question is how do they *apply* the glue to the layers? I have to be super careful when I use CA glue for 2 reasons -- 1) it cures in seconds, and 2) it's very difficult to get just the right amount for each location. If I use too much I have to clean it off with acetone and hope it doesn't smudge. To complicate things the perimeter isn't just one large contiguous surface, it's a rectangle that goes around the perimeter of the circuit, just like tablets are held together.
I've seen a glue "roller" used to apply a very thin layer of glue, which would seem to solve many of the problems, but I don't know what it's called or what its characteristics are. Another option seems to be to order super-thin double-sided tape, and either cut it to the exact shape you need, or order it pre-cut. There are a TON of "3M Double-Sided Bonding Tape" types. This seems to create its own set of problems, since you have to use tweezers and align it just right, and most types are a bit too thick.
Does anyone have any experience with these adhesives and/or construction of layered designs? I'd be grateful for any tips.
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